Speed reducing mechanism for driving airplane propellers



Aug. 20, 1935.

SPEED REDUCING MECHANISM FOR DRIVING AIRPLANE PROPELLERS Filed March 17, 1935 SI wu c/wk n 7707171417 Ji 91'! 2mm 7 a I); 4 V

Patented Aug. 20, 1935 PATENT OFFICE SPEED REDUCING MECHANISM FOR DRIV- ING AIRPLANE PBOPELLEIS Norman E. Gilman, Indianapolis, Ind., assigner to General Motors Corporation, Detroit, Mich, a corporation of Delaware Application March 17, 1933, Serial No. 661,3!

1 Claim.

My invention relates to speed reducing gearing used in association with an internal combustion engine designed, especially, tor driving airplanes,

although the same is equally capable oi use in any servicewhereinashait istobe drivenataspeed lessthanthatotthecrankshaitoianengine; and the object of my invention is to provide improved speed reduction gearing oi the internal gear type wherein the internally toothed gear which drives the propeller shaft is better and ,more eflectively supported and held in position relative to the crank shalt gear than has heretoiore been the case, to provide tor the driving 0! the valve m of the engine and various auxiliary devices thereof from said internal gear. and to provide other improvements in and associated withsuchspeedreducinggearingaswill hereinaiter and at length appear.

The drawing submitted herewith illustrates the preierred iorm of my invention. and the features wherein the same consists are particularly pointed out in the concluding claim.

In the drawing:

Figure 1 is a iragmentary sectional view show- Pigure2isaviewshowingasectionupona verticalplaneindicatodbytheline 2-2.1"lgure1.

Theengineisatwelvecylinder case sections liein aslngle vertical catedbythenumeralll.

Becuredtotheendsoitheaankcase sections alongtheplanell isahousing llhavimahearingatitsirontend II torapropellershait l4 arrangedwithinthehousinmandwhichcarriesa propeller,notshown. 'lherearendotthisahatt hasaiiange |I,andthenumeral ltdesignatesan The (CI. ll-889) crankshaitlhasagear ll uponitsirontend which meshes with the internal teeth of the gear It, to thereby drive the same and. the shaft I.

the propeller carried thereby as will be understood.

The periphery oi the gear II is cylindrical form and rotateswithin and is supported by a continuous single piece bearing ring II, which inturnissupportedinailxedpositionwithin the crank case. In the tom 0! my invention illustrated this bearing ring is clamped between two seats ll, 20 iormed one in eachoi the crank case sections, and which seats are located within the crank case and are associated with the front transverse webs which support the front end of the crank shalt; said seats thus providing a continuous circular support for the bearing ring and withinwhichsaidringisheld. Thebearingring. therefore, provides a continuous and uninterrupted support tor the internal gear it throughout its entire circumierenee. and a supportasclose aspossibletotheinternalteeth thereof. b 4

This term of support locates the ilxed abutment '(thebearingringandtheseats ",Il) ascloseas possibletotheoriginoitheiorce (duetoengagementbetweentheteethotthegearsll, It) actingupontheinternalgeanandwhiehioroeis transmitted to the bearing ring and resisted thereby; and provides a more rigidsupport, and maintains a more definite and permanent relationbetweenthegearsll, llthanisprovidedby baILroIIerorothertypesotbearingsheretotore usedinsimilarrelations. Thetwogearsmay therefore be formed with reierence to and installed withaminimum oi clearance. the hearing ring maintains the parts always in their definite position of initial adjustment. The annulargearandthebearingrlngbeingbothot steel it follows that they expand (due toheating ottheengine) andcontractatthesamerate,and that the clearance initially provided ior between theteethwillbethesameatailtemperatures. Thebearingringasaboveappearsis'commonly madeoisteeLandthesameisshownasprovided with a thin layer II oi plastic bronze, Babbitt metal, or; equivalent anti-i'riction bearing metal alloywhtchisintegrallyunitedtherewitmashy beingtusedtheretqthisbeingtoseeureabetter bearlngbetweenthepartsaswillbeappreciated. Thebearingringisclampedbetweentheseatsll, 2lwithinthecrankcasesectionsl,lmdispreventedi'rommtatingbyapinntheendoiwhich entersaholeinthering. Thebearlng lliorthe erankshatt'isasstatednmtedinsemi-circular seats provided in transverse webs in the crank case sectionsi, I, and the seats I9, which support the bearing ring I8 are as shown formed integrally with said webs. This feature provides reduction gearing wherein alignment of and the spacing between the axes of rotation of the crank shaft and of the bearing ring is permanently maintained, and cannot be affected by disassembling and reassembling the parts, the housing l2 being entirely independent of the said bearings; and provides further a speed reducing device wherein the gear I6 and pinion I! may be so designed as to secure minimum back lash between their teeth and wherein proper meshing and tooth action is maintained when the device is in operation.

The internal gear I6 is provided also with external teeth 23 which mesh with and drive a pinion 24 upon a short internally splined shaft 25, the ends of which are supported in bearings located inside the upper crank case section 6; one bearing 26 extending upward from the upper seat I! for the bearing ring, and the other 2'l being supported beneath the central part of the top wall of said section. The short shaft 25 has a splined driving connection with a long shaft 28 which extends lengthwise of the crank case and is arranged just below the top wall thereof, and to the rear end of the engine where it acts to drive the valve mechanism of the engine, the electrical igniting apparatus, a centrifugal supercharging pump, the oil pumps and such like auxiliary apparatus not herein disclosed in detail.

This shaft it will be appreciated lies between the lower ends of the two cylinder blocks and inside the crank case. Its speed is immaterial so long as the ratio between the crank shaft 9 and the cam shafts which operate the engine valves is two-to-one, so as to secure the operation of the engine upon a four stroke cycle.

Having thus described and explained my invention I claim and desire to secure by Letters Patent:

In speed reducing gearing of the class described and in combination with a crank case, and a crank shaft rotatable in bearings within said case; a housing secured to the front end of said crank case and having a bearing for a propeller shaft; a propeller shaft extending through said housing and rotatable in said bearing; an annular internal gear secured to the inner end of said propeller shaft to drive the same; an integral single piece bearing ring surrounding and in contact with said internal gear to thereby provide direct support therefor; a support for said bearing ring, the same being located within said crank case; a short shaft supported in bearings within the upper part of said crank case; a pinion upon said shaft to drive the same; external teeth upon said internal gear and which teeth mesh with said pinion; a long shaft within the upper part of said crank case and extending longitudinally thereof, and the front end of which has a splined driving connection with said short shaft; and a gear carried by said crank shaft and in mesh with the teeth of said internal gear to thereby drive said propeller shaft.

NORMAN H. GJLMAN. 

